1996 E300D W210 Random Electrical problems - Page 2 - PeachParts Mercedes-Benz Forum

GregMN · #16 09-21-2013, 12:41 PM

The lamp goes out.

In the fuse box with the key in the ACC position:
1 - 7.3 volts, lighter
2 - 7.3 volts, garage door opener
3 - 7.3 volts, wipers
4 - 12.5 volts, instruments
5 - 12.5 volts, turn signals
6 - 12.5 volts, info. center
7 - 6.8 volts, instruments
8 zero

12 - 7.3 volts, seat heater, rear blind
13 - 7.3 volts, radio
14 - 6.8 volts, central control unit
15 - 6.6 volts, ?
16 - 6.6 volts, mirrors
17 - 12.5 volts, diag. socket

funola · #17 09-21-2013, 01:00 PM

Quote:

Originally Posted by GregMN

The lamp goes out.

In the fuse box with the key in the ACC position:
1 - 7.3 volts, lighter
2 - 7.3 volts, garage door opener
3 - 7.3 volts, wipers
4 - 12.5 volts, instruments
5 - 12.5 volts, turn signals
6 - 12.5 volts, info. center
7 - 6.8 volts, instruments
8 zero

12 - 7.3 volts, seat heater, rear blind
13 - 7.3 volts, radio
14 - 6.8 volts, central control unit
15 - 6.6 volts, ?
16 - 6.6 volts, mirrors
17 - 12.5 volts, diag. socket

If you post a link to your fuse wiring diagram, I may be able to tell you where to look next. On the w123 the light switch feeds the fuse panel. You got a trace the fuse panel back to the battery. Maybe just a loose connection on the way.

97 SL320 · #18 09-21-2013, 01:11 PM

OK, the light going out shows we are losing power from the positive side.

From what I recall, MB made use of power distribution blocks under the drivers side dash / kick panel area. I'd have a look there for a burnt connector. A wiring diagram would speed things along as we can trace the affected circuits.

GregMN · #19 10-15-2013, 07:05 PM

It seems to be every circuit that is controlled by the ignition switch.
If I put a jumper wire, in the fuse box, between a full 12v circuit and one of the "weak" circuits (today "weak" is 4.3 volts) all of the weak circuits come on full power.

Is it possible that the ignition switch itself is not making good contact ?
Exactly what happens on the circuits controlled by the ignition switch when the switch is turned ?
Does it send a signal to another device to power the circuits ?
or does the switch directly control the power to all the switched circuits ?

97 SL320 · #20 10-15-2013, 07:58 PM

The ignition switch handles many circuits, only a few are remotely controlled by a relay.

When back feeding a circuit, be sure that the feed had a large enough fuse to handle what you are going to. Also be sure to feed from the "dead" circuit from the common rail and not the fused side of the circuit as all loads will be going through that fuse. Worse case is that the fuse clears and needs replaced.

You will need to probe the ignition switch connector for low voltage, if a feed to the switch is low the problem lies between that connector and battery. If the outgoing wire is low, the switch is bad. Sometimes the switch will fail and burn the connector so be sure to check both.

NEED A WIRING DIAGRAM !! !

scotrvmarine · #21 10-22-2013, 11:20 AM

99 MB E300D I have had the same ongoing issue. I am sure it is the ignition switch. If I wiggle the key the sunroof, horn, door locks etc. all will work. I can hear a clicking sound from the ignition switch when doing this.

As this is an IR switch not sure how the replacement goes on it as in does it need to be programmed etc. to the key.

Scot

GregMN · #22 10-22-2013, 02:10 PM

Did I find the cause and fix the problem: No

Did I make the car work : Yes

I suspect the ignition switch, but I did not remove it to take it apart to see if that is the problem.

I found a circuit that powers "on" with the key in position #2. I put a jumper between the power block side of that circuit to the power block side of the wiper circuit.
When I get some time, I will replace the direct jumper with a relay.
When I get more time, I will rent or purchase the tool needed to remove the locking ring on the ignition assembly and check that out.

Odds are pretty good that I will get around to installing a relay.
If that address the problem, with no further degradation of functions, then the odds of me every pulling the ignition switch are pretty low.

Wiggling the switch on my mechanical, key operated, ignition assembly did not change anything. For me, repeatedly turning the key off and on would usually eventually result in a "good" connection. Sometimes a "bad" connection condition would change to a "good" condition part way through a trip and vise versa.

jay_bob · #23 09-17-2014, 02:57 PM

I suspect the key switch as well.

Unfortunately as you have determined already that the key switch module is a tough thing to replace.

The lock ring needs a special tool.
The part is $$$$$ and is a Theft-Relevant Part so extra hassle at the dealer.
It has to be coded with Star DAS so you will need a dealer or indy that has the software.
The key switch is not only an electrical switch, it is the gateway between the body CAN and powertrain CAN buses.

I've never had the switch apart on a 210. I wonder if the rotating part that has the electrical contacts has been made separate from the computer part of the switch. I would look at EPC and see if that is so. Similar to the way the 12x switches are, the lock part and the electrical part are two pieces. If that is the case maybe you will get lucky.

Maybe if you find one in a junk yard you can disassemble it and see what is going on with the power switching part. Maybe you will get lucky and the power part is easily separated from the logic part. I would definitely experiment on a junkyard switch. I know the 96 and into 97 they used the metal key, you will need a 98 or newer.

However that switch technology has been used all the way up to current models so you may be able to find one in a later 210, 202, 163, etc. I know that my wife's 2008 has a similar lock to my 1998 so there ought to be plenty of examples in yards (although I'm sure the part behind the panel has changed in the mean time so I would stay in the early 2000s). Also I don't think there is any distinction between gas and Diesel (unlike the 12x) because the 210 and later Diesels have electrical fuel control instead of vacuum.

If not I would carefully apply a relay to take the place of the likely burnt contact in the ignition switch. I would isolate that contact from the switch because the current will divide between the bad contact and the relay. Probably 80/20 but the contact will still heat up under load.

For anyone else reading this: 7 V on a bus under load is a danger sign. There is only one explanation of how you can go from 12 V to 7 V, that is because of series resistance. That resistance is in an place that it should not be. That much voltage drop is probably producing multiple tens of watts of heat on something that should not be getting hot. The risk of fire, with no fuses blowing, is very real.

GregMN · #24 09-17-2014, 05:23 PM

Quote:

Originally Posted by jay_bob

I know the 96 and into 97 they used the metal key, you will need a 98 or newer.

Jay,

Thanks for your input. My car is a '96. Does that make any difference in your response ?

Thanks,
Greg

barry12345 · #25 09-17-2014, 05:52 PM

May get by with what you propose. The issue is it may still deteriorate further . If the car is used on long trips at all. I would isolate the exact cause before deciding anything.

Is your model one with a marginal original wiring harness for example?

jay_bob · #26 09-17-2014, 08:38 PM

Oh you have a 96, for some reason I thought you had a 99.

Well then you have it a little easier, the key switch is the metal blade kind, and likely without the DAS chip. There are two key switch assemblies, one with DAS and one without. You need the one that is correct for your car. Jeremy5848 had this problem where they tried to sell him the DAS switch when he had the non-DAS switch. In fact I would reach out to him, that may be the reason he had to replace his switch.

I would instead look at the JY for a 96 with the metal blade key type switch.

You do raise an interesting point on wiring harness, that may be a factor. But I thought they had figured that out by the time the W210 rolled around, but maybe yours was still bio-wire, especially with a first-year 210.